/Engine/Source/Runtime/Core/Public/Math/Vector.h
See if two planes are coplanar. They are coplanar if the normals are nearly parallel and the planes include the same set of points.
true if the planes are coplanar, false otherwise.
static bool Coplanar ( const [TVector](API\Runtime\Core\Math\TVector)< T > & Base1, const [TVector](API\Runtime\Core\Math\TVector)< T > & Normal1, const [TVector](API\Runtime\Core\Math\TVector)< T > & Base2, const [TVector](API\Runtime\Core\Math\TVector)< T > & Normal2, T ParallelCosineThreshold )